Hopper feeders of various kinds are presently available, but none has the degree of versatility and reliability that will permit their use as multi-purpose feeders for such widely varying types of articles as thin cards or envelopes on the one hand and bulky, voluminous newspapers on the other hand. For example, various types of bottom feed devices are available which utilize pins to impale the lowermost article in order to obtain a firm grip thereon as the feeder is moved forwardly in a feeding stroke. However, such an arrangement is not satisfactory when thin, single sheet articles are fed because the pins have a tendency to penetrate not only the lowermost article, but one or more above the lowermost article as well, thereby resulting in multiple feeds of the articles instead of the desired single or successive feeds thereof. On the other hand, in some city newspapers where the outermost jacket is simply used to receive a loose, side-by-side collection of other sections within itself, although the pins may be successful in properly engaging only the outermost article, the lack of cooperating interleaving between the outer jacket and those sections therewithin, coupled with the tremendous friction and weight of those newspapers above it in the stack, may cause a tendency for the pins to simply roll forwardly the lower half of the outer jacket while the contents of the jacket stay behind, thereby failing to feed the entire newspaper and resulting in frustrating, time consuming jam-ups of the equipment.
Vacuum separaters and feeders are likewise suitable for many situations, but, once again, they can have a tendency to adhere to only the outer half of the jacket on voluminous newspapers having loose collections of other sections therein as described above, resulting in the same type of feeding problems. Moreover, if thin, single sheet articles are attempted to be fed at the other extreme, the vacuum can "bleed through" to the next article above so that proper separation does not occur and more than one article at a time is fed.
Other types of machines utilize flat blades or the the like that are disposed on opposite sides of the lower newspaper in the stack and are slipped into the newspaper between an accessible set of pages thereof to thereupon move forwardly and pull against a fold line at the leading edge of the newspaper whereby to accomplish the appropriate feeding and separating action. While this arrangement performs well in most newspaper feeding situations, it is not suitable for single sheet articles or even multi-page articles having only a few, superimposed pages. In such latter circumstance, it is quite difficult to properly adjust the height of the blades such that they can discriminate between the leaves or pages of one article and those of the next article thereabove to the end that misfeeding can and does occur.
Certain card or envelope feeders of the type shown in U.S. Pat. Nos. 3,053,176 and 3,230,871 utilize rotary devices at the bottom of the stack having peripherally disposed friction pads or the like which wipe against and feed forwardly the lowermost envelope during each revolution of the device. This tangential type of point contact between the pads and the envelopes has not been found to be satisfactory when attempts are made to utilize this principle in connection with bulky newspapers.
Another type of envelope feeder sold under the trade designation "Postalia" by the Tele-Norm Corporation of New York utilizes a belt-type conveyor at the bottom of the stack, which conveyor has an upper stretch which is raised and lowered at certain fixed intervals while driven forwardly, thereby rising against and forwardly feeding the lowermost envelope before then returning to its retracted condition at a predetermined instant when the cam lobes associated with drive pulleys of the conveyor rotate through the next part of their revolution. While such a belt conveyor type arrangement coupled with raised pressure engagement by the belt on the lowermost article provides an effective separation means for envelopes and single sheet articles, it would not be satisfactory in connection with the handling and feeding of bulky newspapers because, among other things, such a preset raising and retraction cycle would not account for the significant slippage which is commonplace when friction feeders are utilized to feed bulky newspapers and the upper papers in the stack weigh heavily upon the lower paper so as to exert a sizeable retaining force that must be overcome if proper feeding is to be achieved.
Consequently, there has simply not heretofore been a feeder having that versatility and flexibility that will permit the same machine to be utilized with equal success for both single sheet feeding as in cards and envelopes, and multiple sheet feeding as in bulky, big city newspapers.